Dampening device



United States Patent 3,347,483 10/1967 Hoag Primary ExaminerLeonard D.Christian Attorney-Brown, Jackson, Boettcher and Dienner ABSTRACT: Adampening device particularly suited for tape tension levers of a taperecorder to prevent excessive tension in the tape which may occur, forexample, in reel startups and stops. The dampening force is acombination of a frictional force and a spring force but only thedifference in the two forces effects a return of the tension lever toits normal play range. A separate spring force is used in the play rangeto isolate reel vibrations or to accommodate minor fluctuations in speedof tape takeup. A retracted position of the levers is provided forloading of the tape and said position is controlled by the position ofthe switch actuator for the main on-off switch.

23 M He II fi lmmm\\\\\ '\\\\\i\ \\z \\l p Q r l Illl'l t- I i e i .32 rfu 1 5 "ll 36c 14 i Patented Dec. 1, 1970 Sheet I DAMPENING DEVICEBACKGROUND AND SUMMARY OF THE INVENTION Heretofore tape tension leversfor tape recorders have frequently relied upon the tension, orcompression, of a spring to relieve excessive tension on a tape. Suchexcessive tension may occur on startups when the supply reel is gettingup to normal speed or if the takeup speed of the reel exceeds the speedat which the capstan can deliver tape. Also if there is substantialbraking of the supply reel before the capstan drive is discontinuedduring a stopping operation, the tape may be placed under too muchtension.

The disadvantage with prior art tension levers which rely upon springsis that, when the spring is tensioned during a lever tensioning movementas the lever yields in response to increased tensioning of the tape,greater and greater energy is stored in the spring. This energy is thensubsequently released and frequently is released in a manner whichresults in a change in the tape speed so that a true recording orreproduction is not possible.

In my invention I employ one spring with each tape tension lever whichspring is effective through a range of movement of the lever which Icall the play" tension range, namely, a range of movement to accommodateminor changes in tape tensioning during a playing or recording operationwhen the tape and reels are up to normal speed. In this range the tapetensioning lever serves to filter out reel vibrations and accommodateminor changes in tape tension. This range of movement of the lever alsocan accommodate excess tape delivered during an initial startup when thecapstan begins delivering tape and the takeup reel is first gainingspeed.

Beyond this play range, I provide what I call a start-stop tension rangesince it is during starting or stopping that the tape may be excessivelytensioned andit is on such occasion that it is necessary to have thetension lever yieldingly resist strong tensioning forces exerted on thetape. In this start-stop range, for example, it may take from to ouncesof force to cause the tape tension lever to be moved through its rangewhereas in the play range one-fourth to 1% or 2 ounces may be all thatis involved.

In the start-stop tension range I employ two structures which afford acombination of forces to produce the total dampening force on each tapetension lever, namely a combination of a frictional force and aresilient force provided by a second spring. I prefer to apportion thesetwo forces so that the frictional force is a high percentage of theresilient force regardless of the variation in resilient force. When thetension lever is moved in the dampening direction in the start-stoprange the combination of the frictional and resilient forces must beovercome, but only the difference in these forces serves to return thetension lever to the play range. Since that is a relatively small force,objectionable acceleration of the tape is avoided as the tape tensionlever is returned to the play range.

In providing these two dampening forces I arrange the structures in sucha manner that in the start-stop range the spring applies force to thefriction-producing structure. The amount of frictional force is notdependent on the velocity of the tension lever or parts associated withit, but, instead, is determined by the amount the spring is tensioned.As the spring force increases, it applies increasing force on thefrictionproducing structure and therefore the relation between the twodampening forces is kept substantially the same throughout thestart-stop tension range.

Since in some types of tape recording activities there is a need forhigh tape speeds and instantaneous" starts and quick stops, thedisadvantage of prior art structures, which rely solely on a spring, isapparent. Substantial energy will be stored in such spring which energywill be released as the tape tension lever is returned to the playrange. In my dampening structure, high tensioning forces on the tape canbe yieldingly accommodated but without permitting the energy storage inthe spring to be directed completely to a return of the tension lever,since most of the stored energy must be employed in overcoming thefrictional force which is only slightly smaller. As a consequence, thereturn of the tension lever to the play range is at a relatively steadyand moderate rate which introduces no errors in recording orreproduction of information on the tape.

A further improvement provided by my invention is in the control of thetape tension levers during loading of the tape. Retraction means servesto hold the levers in an alined position while the tape is lead from thesupply reel to the takeup reel past the heads, tape guides and tapetension levers.

Yet a further improvement resides in my provision of an onoff switch forthe drive motor, with the switch and retraction means for the leversbeing jointly actuatable whereby the retraction means are released totheir nonretracting position when the switch is actuated to its "on"position.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS FIG. 1 is adiagrammatic top plan view of a tape recorder which has a pair of tapetensionlevers which are dampened by the dampening device of myinvention;

FIG. 2 is a view similar to FIG. I. but enlarged and fragmentary andpartly broken away to expose portions of the tape tension levers andcertain associated parts, with the tape tension levers shown in aretracted position suitable for loading of the tape;

FIG. 3 is a view similar to FIG. 2 but with different positions guideportion 13 of a tape tension lever 14 (FIG. 2) and past a series of tapeguides 15a, 15b and 15c, capstan 16 and a head bar 17 carrying heads 18and 19 and pressure roller 20. From there the tape 11 extends around aguide portion 13 of a second tape tension lever 14' (FIG. 2) and then toa takeup reel 21. Arcuate slots 22 and 22' are formed in the top plate23a of the deck 23 (FIG. 2) and accommodate arcuate movement of the tapeguides 13 and 13' of the tape tension levers 14 and 14'. As indicated bythe legend on FIG. 1 the tape tension levers have a play" tension rangeand a start-stop tension range, a load position and, in the case oflever 14, an end-of-tape position. A switch actuator in the form of acontrol knob 24 controls the main on-off switch 25 (FIG. 2) and also,through structure to be described below, controls the load position ofthe tape tension levers 14 and 14'.

As may be seen from both FIGS. 2 and 3 the shaft 26, to which thecontrol knob 24 is secured, is rotatable in a bracket 26a and isconnected with a bellcrank lever 27, one arm 27a of which is pivotallyconnected with retraction means 28 for tape tension lever 14 and theother arm 27b of which is pivotally connected with retraction means 28for tape tension lever The retraction means 28 and 28' are straps eachhaving a body portion 28a with a slot 28!; adapted to be guided by pins29 and 29 respectively. The pins 29 and 29' are supported from deck 23.Each retraction means also has a projection 280 at its end adapted toengage a short stud 14a of the tension lever 14 or 14'. Studs 14a areconnected with the counterweight portions 14b of the tape tension leversand the levers are pivotally supported by their shafts for rotation inhollow bearing posts 14d (see FIG. 4) which posts are supported by thedeck 23. Shafts 14c may be retained in position by snap rings 14f. Ahollow stud lde positioned below each tape tension lever extends downaround the hollow bearing post 14d and spring lever arms such as 30 and30 are rotatably mounted on the lower ends of the hollow studs Me. Eachof the tape tension levers 14 and 14' has a small down turned rotationof the spring lever arm or 30. l

The spring lever arms30 and 30. at their outermost ends have studs 31and 31', respectively, which studs pass through arcuate slots 23b and23c in the deck 23 and are pivotally secured as at 31a to movablemembers 32 and 32', respectively, in the form of dampening slides. Itwill be seen that if tape tension lever 14 rotates in a clockwisedirection its flange 143 will engage the finger 30a of spring lever arm30 and cause the latter to rotate clockwise and thereby cause movementof the dampening slide to the right as viewed in FIGS. 2 and 3. A

similar movement of dampening slide 32' to the left may take place inresponse to counterclockwise rotation of spring lever arm 30' and tapetension lever 14'. The other end of each slide has a slot 32a which fitsabout a yoke stud 33 and is slidable thereon and pivotally movablethereabout. Studs 33 and 33' are secured to the underside of deck 23.

Below the slides 32 and 32 there are mounted on the studs 33 and 33'yokes such as 34 and 34' each of which is pivotally swingable around itsrespective yoke stud 33 and 33'. The yokes are secured on thestuds bywashers 35 and 35', respectively. Each yoke has a pair of spacedapertured flanges 34a and 34b for supporting a yoke pin 34c on which pina pivotal member, such as bellcrank lever 36, is supported by a pair ofspaced, apertured flanges 36a and 36b. integrally formed with theflanges 36a and 36b is one arm 36c of the bellcrank lever 36, the otheram being designated by reference numeral 36d. At the outer end of thearm 360 are a pair of spaced flanges 36c and 36f which straddle thedampening slide 32. Accordingly, when the dampening slide is rotatedaround the yoke stud 33, it will cause the pivotal member 36 to pivotwith it, which action is possible because member 36 is carried on thepivotal yoke 34 which is also mounted on yoke stud 33. Although I havedescribed the foregoing structures by reference to the structure on theleft side of FIGS. 2 and 3 it will be understood thatcorrespondingstructure and similar reference numerals are on the right side of F 16$.2 and 3.

Spring means 37 in the form of a tensioned spring is connected at oneend with the pivotal member 36 at an aperture 36g in arm 36d. A seriesof apertures similar to 36g may be spaced along the arm 36d to providediffering locations for connection of the spring 37 to the arm 36d ofpivotal member 36 to vary the tension in the spring. The other end ofspring 37 is secured in an aperture 32b in the bent end 320 of thedampening slide 32 which is rotatably mounted at 31a on the stud 31 ofspring lever arm 30. The latter, inturn, is operatively associated withthe tape tension lever 14. If preferred, the spring 37 could be formedof a plurality of shorter interconnected springs. Spring 37 is slightlytensioned and, when stretched, provides an increasing dampening force.

Frictional elements 38 and 38', each in the form of a frictionalpad-which may be made of cork, cork and rubber composition, or someother suitable frictional material-are connected with the respectivearms 36c of pivotal members 36 and 36'. Pads 38 and 38' engage theundersurface of the dampening slides 32 and 32' and are urged intoengagement with the slides by the respective tension springs 37 and 37pulling on arms 36d of pivotal members 36 and 36. On the opposite sidesof the dampening slides 32 and 32 are disposed second frictionalelements 39 and 39' each in the form of a washer (of the same or similarmaterial as pads 38 and 38') which engages the dampening slide and theundersurface of the deck 23 and surrounds the stud such as 33 or 33.

Coil springs 40 and 40 have one end bearing against the spring leverarms 30 and 30' and the other end bearing against the body of the tapetension levers 14 and M, respectively, with the coils of the springsencircling the hollow studs Me. These springs 40 and 40' act to urge thespring tension levers 14 and M downwardly, or forwardly, as viewed inFIG. 1 of the drawings throughout a range of movement referred to as theplay tension range. The force exerted by each of these springs'may be inthe range of one-fourth l0 1% or 2 ounces. it is substantially less thanthe force of springs 37 and 37' which act on the tape tension levers 14and 14 throughout the stop-start" tension range. Springs 37 and 37'. forexample, may exert a force of from 10 to 20 ounces.

Spring as which urges the tape tension lever 14' in a clockwisedirection permits the tape tension lever to accommodate an excess amountof tape which may be delivered when, for example, the tape recorder isstarted up and the capstan is immediately delivering tape before thetakeup reel 21 reaches sufficient speed to take up the tape in thenormal manner. Since the takeup reel does not go from zero speedprecisely up to the desired takeup speed but,instead, will tend toexceed the desired speed at least momentarily after startup, then,immediately after tape tension lever 14 has taken up the excess tapedelivered from the capstan 16, a condition will develop in which thetakeup reel reaches a speed where it exceeds the speed at which thedrive capstan i6 delivers tape. This will cause a tension in the tapeand the tape will bear against the tape tension lever 14 and urge itinto its startstop" tension range, whereupon lever 14 will engage androtate spring lever am 30 which will in turn cause dampening slide 32'to be moved, spring 37 to be stretched and friction to be developed bythe frictional elements 38' and 39 engaging the dampening slide 32'which is moving. The resulting dampening action will prevent the tapefrom being tensioned excessively. However, such-tension as develops hasa braking effect on the takeup reel and may momentarily slow down thereel to a speed slightly less than the desired takeup speed, with theresult that, momentarily, the amount of tape delivered by the capstan 16may somewhat exceed the reels ability to take it up. Because the forcesof spring 37 and the frictional elements 38 and 39 are cumulative in thedampening direction, but it is only the difference between the springand frictional forces which will move the tape tension lever 14' backtowards its play tension range, the action of spring 37 cannot be reliedon alone to cause movement of tape tension lever 14' to absorb theexcess tape since it might not be able to act quickly enough. However,tape tension lever 14', with the assistance of spring 40' can movequickly enough in a clockwise direction to take up the slack since tapetension lever 14' is not connected directly to slide 32' and to spring37 and spring lever arm 30' but is merely in engagement with springlever arm 30' through its bearing against the latters finger 300. Whenthe foregoing condition of excess tape exists momentarily-and whilespring tension lever 14 is taken it upthis results in less brakingaction on the takeup reel so that it can speed up to its desired speed.While it will be readily understood that there may be alternateconditions of underspeed and overspeed of the takeup reel 21 severaltimes in the first moments of startup, these will not result inovertensioning of the tape or in significant fluctuations in speed ofthe tape past the heads 18 and 19, because the tape will be kept undertension, within a proper range, at all times.

During the playing or recording of the tape, tape tension levers l4 and14' will have positions at or near their load positions and springs 40and 40 will accommodate minor fluctuations in tape tension during tapetakeup. However, when the tape has been played completely and the end ofit has left the supply reel and it has passed from between the capstan16 and pressure roller 20, it will no longer maintain a force againstthe tape tension lever 14', and spring 40' will cause the lever to moveclockwise, as viewed in the drawings, to its most clockwise position(see end-of-tape position in FlGS. l and 3) at which time the stud 14awill rotate sufficiently clockwise to engage the switch arm 41a of theout of-tape switch 41 and move it counterclockwise to thereby open theswitch and the circuit to the motor which drives the capstan, therebyshutting off the capstan motor, and also opening the circuit to motorsassociated with the takeup and supply reels and the circuit which holdsthe head bar 17 up against the tape. If the tape is then to be rewoundonto the supply reel, or if a new tape is to be immediately played andthe played tape removed, the user will turn the control knob 24 of themain on-off switch to the off position which movement will cause theretraction means 28 and 28', through their respective end projections28c to engage the studs 14a of the tape tension levers l4 and 14' androtate them to their load positions.

OPERATION Assuming that the tape recorder is in a shutoff condition,knob 24 of the main on-off switch will be so positioned that its shaft26 and arms 27a and 27b of the bellcrank lever 27 will have moved theretraction means 28 and 28' to the position shown in FIG. 2. Arm 27b insuch position will have pressed the switch contact arm 25a in acounterclockwise direction to thereby open the circuit. It will befurther assumed that the controls (not shown) of the usual type foroperating the tape recorder are in the stop position so the head bar 17will be in its withdrawn position as shown in FIG. 1. The user will thendispose the tape 11 around the guide portion 13 of tape tension lever 14and past the guides 15a, 15b and 150 and the capstan 16 and then aroundthe guide portion 13' of tape tension lever 14' to the takeup reel. Whenthe main on-off switch is actuated to on" position by turning the knob24 clockwise as viewed in FIGS. 1 and 2, the retraction means 28 and 28will be moved to their positions shown in FIG. 3 to permit the tape tobe played. At this time springs 40 and 40' will be urging the tapetension levers l4 and 14' into engage ment with the tape 11.

When the play or record button or lever (not shown) is actuated, thehead bar 17 is moved so that the heads 18 and 19 engage the tape and thepressure roller 20 engages the tape against the capstan 16. Tape 11 isthen immediately driven to the right as viewed in FIG. 1 and tension isapplied to the tape and the tape presses against the tape tension lever14 through the latters guide portion 13 since the supply reel does notimmediately come up to full speed. In this way a few inches of slack canbe supplied, as the tape tension lever 14 yields, in order not to placethe tape under undue tension. When the guide 13 of tape tension lever 14is thus pressed by the tape 11 in a clockwise direction, the flange 14gat the counterweight end of the lever 14 engages the finger a of springlever arm 30 and will thereby cause the spring lever arm 30 to rotate ina a clockwise direction and will thereby cause the dampening slide 32 tobe moved generally toward the right with its slotted end 32a pivotingaround the yoke stud 33 thereby causing the dampening spring 37 to bestretched. The foregoing parts provide a first dampening structure. Asecond dampening structure is provided by the dampening slides lowersurface engaging the friction pad 38 which is being urged against it bythe spring 37 acting through the bellcrank lever, or pivotal member, 36.The frictional element 38, along with the frictional washer 39, therebyintroduces a frictional dampening force at the same time that adampening force is provided by spring 37 which is being stretched as thedampening slide moves in its dampening direction in response to movementof the tape tension lever 14.

For purposes of maximum illustration, various positions of the tapetension levers l4 and 24' are shown in FIG. 3. The left side of thatFIG. shows the tape tension lever 14 together with the associated firstand second dampening structures, in their maximum dampening position,although this extreme position is not usually reached. At the right sideof FIG. 3, the tape tension lever 14' is shown in full lines at atypical play position, but it will be understood that it also can bemoved to a comparable maximum dampening position approximately 90 fromthe load position, or to some intermediate position in the stop-starttensioning range. Such dampening action may take place, for example,when the takeup speed exceeds the speed at which type is fed from thecapstan.

FIG. 3 demonstrates the difference in tension provided by the springs 37and 37' when in the substantially untensioned play position (right sideof FIG. 3) and in the dampening position (left side of FIG. 3). As thetape tension lever M, or 14' is moved increasingly in the dampeningdirection, sometimes referred to as the first direction, the spring 37or 37' becomes increasingly tensioned and therefore increases thedampening force. As can be readily seen from FIG. 4, the increase intensioning of spring 37 causes it to act through the bellcrank lever 36to also increase the pressure of the cork pad 38 against the dampeningslide 32, thereby increasing the frictional dampening force as well.From this arrangement, it will be seen that the resilient, or spring,dampening force and the frictional dampening force will both increaseand decrease together and the spring force is selected to be greaterthan the frictional force. It will be observed that a part of thefrictional force provided by the dampening mechanism is provided by thefrictional washer 39 which lies on the opposite side of the dampeningslide 32 from the frictional pad 38. The total frictional force may, forexample, be approximately percent of the spring force.

It is the difference between these two forces which then returns thetape tension lever in a relatively even and moderate manner to the playposition. Were the tape tension lever to be dampened solely by a spring,it can be readily appreciated that the energy stored up in such springcould, when released, move the tape too rapidly. This could result in afailure to make a true recording or reproduction of information.

It is possible to vary the spring tension by substituting spring ofdifferent characteristics, but it is also possible to vary the springforce by connecting an existing spring at a different location along thearm 36d of the pivotal member (bellcrank lever) 36.

As can be seen from comparing the left and right side of FIG. 3, whenthe spring 37 is fully stretched the associated spring lever arm 30 hasbeen rotated approximately 90 from its initial position which was likethat shown on the right side of FIG. 3. During the time when springlever arm 30 was rotating to the position shown on the left side of FIG.3 and was moving slide 32 and thereby causing spring 37 to be stretchedan increasing amount, the slide, 32 and spring 37 were pivoting aroundyoke stud 33 (see FIGS. 3 and 4) and swinging closer to the axis ofrotation "of spring lever arm 30. As a result, toward the end of itsrotation spring lever arm 30 moves slide 32 and stretches spring 33 at aslower rate. This provides a desirable dampening action without reducingthe total dampening force, since the dampening force continues toincrease (but less rapidly) by reason of the continuing stretching ofthe spring 37 and its action of increasing the frictional engagement ofthe pad 38 and washer 39 with the surfaces of the slide 32.

While I have shown a preferred embodiment of my invention, I do notintend to be limited thereto, except as the appended claims are solimited, since modifications will readily suggest themselves to oneskilled in the art who has my disclosure before him.

I claim:

1. In a tape tensioning system having at least one tape tension lever,force producing means acting on said lever through one portion of itsrange of engagement with the tape, and second force producing means of agreater total strength acting on said lever through a second range ofits engagement with the tape, the second force producing means includingthe combination of frictional force imparting means and resilient forceimparting means separate from said first force producing means.

2. The invention of claim 1 wherein the tensioning system has a pair oftape tension levers each having the same kind of force producing meansacting on it, together with lever retraction means adapted to hold saidtape tension levers inan alined position during loading of the tape.

3. The invention of claim 2 together with an off-on switch and means foractuating the switch, said actuating means being operatively associatedwith said lever retraction means and adapted to actuate the leverretraction means to its retracting and nonretracting relationship withsaid tape tension levers.

4. The invention of claim 3 wherein said actuating means actuates theswitch to .on position and actuates the lever retraction means at thattime to its nonretracting position relative to said tape tension levers.

5. Dampening means for a movable device which is adapted to be engagedand moved in a first direction by force exerted by a tensioned tape,said dampening means comprising first and second structures, said firstand second structures providing cumulative forces serving to dampen themovable device when it is moved in said first direction and providingdifferentially related forces when the force exerted by the tape isrelieved for moving said movable device in a second direction.

6. Dampening means for a movable device as claimed in claim 5, saidfirst structure providing a dampening force by frictional means and saidsecond structure providing dampening force by resilient means.

7. The invention of claim 6 wherein the dampening force provided by thesecond structure is greater than the dampening force provided by saidfirst structure.

8. The invention of claim 6 wherein the resilient means comprises aspring structure adapted to urge said movable member in a seconddirection when the force exerted by said tensioned tape is relieved.

9. The invention of claim 6 wherein the dampening force of saidresilient means increases as said movable device is increasingly movedin said first direction.

10. The invention of claim 6 wherein the resilient means varies thedampening force of said frictional means as said movable device ismoved.

11. The invention of claim 6 wherein the resilient means increases thedampeningeffect of said frictional means as said movable device isincreasingly moved in said first direction.

12. The invention of claim 6 wherein the dampening force provided by thefrictional means is a high percentage of the dampening force provided bythe resilient means.

13. The invention of claim 6 wherein the dampening force provided by thefrictional means is approximately 90 percent of the dampening forceprovided by the resilient means.

14. The invention of claim 6 wherein the rate of change of the totaldampening force provided by said first and second structures decreaseswhen the movable device is moving in said first direction and approachesits maximum displacement.

15. Dampening means for a movable device which is adapted to be engagedand moved in a first direction by a tensioned tape passing from a sourceof supply to a takeup device, said dampening means comprising a firststructure and a second structure both serving to dampen movement of saidmovable device when it is moved in said first direction by force exertedby said tensioned tape, said first structure providing a dampening forceby frictional means and said second structure providing a dampeningforce by resilient means, said first and second structures beingeffective through one range of movement of said movable device and saidmovable device having a second range of movement, together with secondresilient means adapted to urge said movable device in a seconddirection in said second range of movement of said movable device.

16. The invention of claim wherein the average force exerted by saidsecond resilient means in said second range of movement is less than atenth of the average total dampening force provided by said first andsecond structures in the first range of movement of said movable member.

17. Dampening means for a tape tension lever which is movably mountedand has one end adapted to be engaged by a tensioned tape as it passesfrom a supply reel to a takeup reel, said dampening means comprisingspring means having one end connected with a pivotal member and theother end connected with a movable member which moves in response tomovement of said tension lever in a dampening direction, said movablemember en.agin a frictional element during movement of said tension ever0 thereby provide a frictional dampening force.

18. The invention of claim 17 wherein the tape tension lever causesmovement of said movable member by pivoting a lever which is operativelyassociated with said movable member.

19. The invention of claim 17 wherein the movement of said movablemember in the dampening direction stresses said spring meansincreasingly to provide an increasing dampening force.

20. The invention of claim 19 wherein the pivotal member, which isconnected with the spring means, acts to press the frictional elementand movable member increasingly into engagement with each other toincrease the frictional dampening force.

21. The invention of claim 2i) wherein the frictional force is a highpercentage of the spring force.

22. Dampening means for a tape tension lever which is pivotally mountedand has one end adapted to be engaged by a tensioned tape as it passesfrom a supply reel to a takeup reel, said dampening means comprisingspring means having one end connected with a pivotal member and theother end connected with a movable member which moves in response tomovement of said tension lever in a dampening direction, said movablemember engaging a frictional element during movement of said tensioninglever to thereby provide a frictional dampening force, the movablemember being a slide, and the pivotal member being another levercarrying the frictional element on one of its arms connecting with saidone end of the spring by the other of its arms.

23. The invention of claim 22 wherein said one end of said spring isadapted to be connected to said one arm of the lever at any one of aplurality of locations along its length.

24. The invention of claim 22 together with a second frictional elementengaging the slide on a side opposite from engagement with said firstmentioned frictional element.

25. The invention of claim 22 wherein the lever which carries thefrictional element has its fulcrum mounted for swinging movement arounda support and said slide is guided by and has swinging movement aroundsaid support, with said fulcrum and slide swinging together.

26. The invention of claim 22 wherein said other end of the spring meansconnected with said slide follows a curved path and the effective lengthof said other lever acting on the slide to stress the spring means isreduced as the tape tension lever is increasingly moved in the dampeningdirection.

27. Dampening means for a movable device which is adapted to be engagedand moved in a first direction by force exerted by a tensioned tape,said dampening means comprising first and second structures, said firstand second structures providing forces which add together to dampenmovement of the movable device when it is moved in said first direction,one of said structures providing a further force moving said movabledevice in a second direction when the force exerted on the movabledevice by the tape is relieved and the other of said structuresproviding an opposing force to dampen the movement of said movabledevice in the second direction.

